Aside the traditional full-thickness Penetrating Keratoplasty (PKP), eyes with permanent endothelial compromise resulting in suboptimal vision can be treated by replacing diseased parts of the cornea while retaining the healthy anterior parts of the cornea.
Posterior Lamellar Keratoplasty (PLK) was proposed by José I. Barraquer and Charles Tillett in the 1950s. The demand for precisely shaped corneal grafts increased in the late 1990s, when it was shown that a surgically resected corneal disc including diseased endothelium can be replaced with a similar partial-thickness donor disc and that the disc can be attached to the inner corneal surface of the patient's cornea without any sutures. This development led to similar surgical procedures based on differently prepared grafts.
For example, Descemet Stripping Automated Endothelial Keratoplasty (DSAEK) uses an endothelial graft, which has been prepared by mounting the donor cornea at an artificial anterior chamber and removing the anterior corneal stroma using a femtosecond laser or a microkeratome. For DSAEK, precut eye bank-prepared endothelial grafts are available, which eliminates the need for preparation of the donor corneal tissue in the operating room. However, deep anterior cuts by means of the femtosecond laser or the microkeratome can result in irregular sections, if the donor cornea is not properly mounted at the artificial anterior chamber. Furthermore, when using the femtosecond laser, the conventional preparation of the endothelial graft may be affected by optical inhomogeneities in the donor cornea, e.g., since typically more than twelve hours have passed post mortem at the time of graft preparation. E.g., the inhomogeneities can affect a focusing precision for the deep cut.
For Descemet Membrane Endothelial Keratoplasty (DMEK), the donor Descemet membrane is scored, partially detached under fluid and trephined from the endothelial side. The Descemet membrane with the healthy donor corneal endothelium is removed as a single donor disc without any donor corneal stroma. Hence, there is no need for an artificial anterior chamber or a microkeratome in the preparation of the endothelial graft. However, manually removing the Descemet membrane and the endothelium by means of mechanical trephination as well as subsequent membrane peeling for DMEK can easily cause irreparable damage to the endothelium, which does not regenerate.